Voltage regulating system



June 21, 1955 M. slsKEL 2,711,507

VOLTAGE REGULATING SYSTEM Filed Dec. 3, 1952 MHNUEJL ESKEL United States Patent VOLTAGE REGULATING SYSTEM Manuel Siskel, Collingswood, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application December 3, 1952, Serial No. 323,786

The terminal 15 years of the term of the patent to be granted has been disclaimed 6 Claims. (Cl. 323-22) unidirectional voltage, the unregulated input voltage is greater than the regulated output voltage. The diierence between the unregulated input voltage and the regulated output voltage is substantially the voltage drop across the voltage regulating system. This voltage drop may be quite substantial where a relatively high degree of f voltage regulation is desired. For example, where an output of 160 volts of regulated voltage is desired for a utilization circuit, it is necessary to apply an input voltage in the neighborhood of 280 volts to the voltage regulating system. In this particular example, the voltage drop across the regulating system is 120 volts.

Voltage regulating systems of the type described comprise a plurality of electron discharge devices, or ampliers, in addition to a degeneratively operated variable impedance control tube. It has been found that a failure of these amplifiers, caused by a burn-out of the heater elements or by low electron emission from their cathodes, may result in causing an excessive amount of voltage to be applied to the utilization circuit. The failure of an electron discharge device in a regulating system, therefore, may damage a sensitive utilization circuit because of the excess voltage applied to it under these conditions.

lt is accordingly a principal object of the present invention to provide an improved voltage regulating system having fail-safe features.

Another object of the resent invention is to provide a novel regulating system by means of which the regulated output voltage is reduced, or cut oft by the failure of any of the electron tubes in its circuit.

Still another object of the present invention is to provide an improved voltage regulating system, which is simple in construction, inexpensive to manufacture, and yet practical and etlicient to a high degree in use.

According to the invention, these and other objects and advantages are attained in a voltage regulating system of the type wherein a lirst degeneratively operated variable impedance electron tube is connected in series between the unregulated voltage supply and the load. In its simplest form, the voltage regulator, in accordance with the present invention, comprises second and third variable impedance tubes each having a heater element. These heater elements are connected in a single series circuit with a source of heater voltage supply. The second tube is connected to the degeneratively operated series control tube and operates as a cathode follower. The third tube is directly coupled to the cathode follower. A sample Voltage proportional to the voltage across the load is derived from the output circuit of the regulator system and fed back to the third tube in such a manner that the impedance of the third tube is varied inversely with the variations in the magnitude of the sample voltage. The sample voltage may be applied directly to the input of 2 the third tube or it may be applied through further amplifying circuits to the input of the third tube.

A better understanding of the invention may be had from the following description of illustrative embodiments thereof when read in connection with the accompanying drawing in which similar reference characters are applied to similar parts and in which:

Fig. 1 is a circuit diagram of a regulating system in accordance with the present invention; and

Fig. 2 is a modification of the arrangement of Fig. l.

Referring now to Fig. 1 there is shown a voltage regulating system having a pair of input terminals 10 and 12 for applying a source of unregulated voltage (not shown) thereto. A pair of output terminals 14 and 16 is provided for a load or utilization circuit (not shown). The voltage output to the load is regulated by a first degeneratively operated variable impedance control tube 18. The tube 18 is illustrated as a duo-triode but it is understood that a single triode or a plurality of triodes connected in parallel may be used depending upon the current requirements desired. The anodes of the tube 18 are connected to each other and to the input terminal 10. The cathodes of the tube 18 are connected to each other and to the output terminal 14. T he input terminal 12 and the output terminal 16 are connected to a source of reference potential or ground. The heater elements 19, 19 of the tube 18 are connected in series with each other and to a source of conventional heater voltage (not shown).

Means are provided in order to sample the output voltage across the load. To this end, there is provided a potentiometer 2i) having one end connected to the output terminal 14 and the other end connected to ground. The variable tap or" the potentiometer 2) is connected to the grid of a variable impedance tube 22. A capacitor 24 is connected between the variable tap of the potentiometer 2@ and the junction between the potentiometer 20 and the output terminal 14. The tube 22 comprises an anode connected to the input terminal 1G, and a cathode connected to ground through a cathode resistor 26. The tube 22 may be an individual triode or a part of a duo-triode of which the tube 28 is also a part. The tube 28 comprises an anode connected to the input terminal 1t) through an anode load resistor 38, and a cathode connected to the cathode of the tube 22. The grid of the tube 28 is maintained at a substantially iixed potential by connecting it to a junction on a voltage divider formed by a resistor 32 and a voltage regulating tube 34 connected across the output terminals 14 and 16. The voltage regulating tube 34 is shunted by a capacitor 36. it will be noted that the tubes 22, 28 are connected in a manner to form a differential amplifier. The heater elements 37 and 39 for the tubes 22 and 2S, respectively, are connected to each other in series, that is, they have one common junction, and across a source of conventional heater voltage (not shown). With this arrangement, it will be understood that a break or open in the heater element of either of the tubes 22 or 28 will result in a cessation of current through the heater circuit of each of the tubes 22 and 28.

The anode of the tube 2S is connected to output terminal 10 by means of load resistor 3i) and connected to ground through a Voltage divider comprising the resistors 33 and riti. The resistor 38 is shunted by a bypass capacitor 42. The output of the tube 28 is directly coupled to the grid of a variable impedance tube 44. The tube 44 comprises an anode connected to 'the input terminal 10 through a load resistor 46, and a cathode connected to the junction of a voltage divider comprising the resistors i8 and 5i? connected between the output ierminals 14 and 16. The output of the tube 4d is coupled directly to the tube 52 by means of a connection between the anode of the tube 44 and the grid of the tube S2.

The anode of the tube 52 is connected to the input terminal 16, and the cathode of the tube 52 is connected to ground through resistors 54 and 56. The junction between the resistors S4 and 56 is connected to the grids of the series control tube 18 through resistors S8 and 60. The heater elements 59 and 61 for the tubes 44 and 52, respectively, are connected in series with each other and across a source of conventional heater voltage (not shown). It is understood that the heater voltage source forms a single series circuit with the heater elements 59 and 61 of the tubes 44 and 52 so that a break in any one of the heater elements will result in a cessation of current through both of the heater elements. A bypass capacitor 62 is connected across the resistor 54.

The operation of the regulating system illustrated in Fig. 1 will now be described. Let it be assumed that there is a tendency for the output voltage across the output terminals 14 and 16 to increase because the input voltage across the input terminals and 12 has increased, or because the impedance of the load has increased. Any increase in voltage, however slight, is fed back to the tube 44 in such a manner that its impedance, that is, the resistance between the cathode and the anode of the tube 44, is decreased. A sample of the increased voltage across the output terminals 14 and 16 is derived by the variable tap of the potentiometer and applied to the grid of the tube 22, thereby increasing the current through the anodecathode circuit of the tube 22. An increase in current through tube 22 causes an increase in the voltage across resistor 26, and, therefore, at the cathode of tube 28. Since the grid of tube 28 is xed by the voltage regulator tube 34, the current decreases and the voltage at the anode of the tube 28 is increased. This positive-going voltage is applied to the grid of the tube 44 whereby its impedance, or plate resistance, is reduced. This results in an increase in the current in the anode-cathode circuit of the tube 44 and there is produced a negative-going voltage at the anode of the tube 44 which is applied to the grid of the tube 52. Consequently, the current through the tube 52 is decreased, resulting in a drop in voltage across the cathode resistors 54 and 56. This latter negative-going voltage is applied to the grid of the series control tube 18, whereby its plate impedance is increased and the tendency for the output voltage across the output terminals 14 and 16 to increase is offset. Any tendency for the output voltage across the terminals 14 and 16 to decrease is offset by a reverse set of conditions. Thus, the output voltage across the output terminals 14 and 16 is maintained substantially constant with tendencies for the unregulated input voltage and the load to vary.

An important feature of the voltage regulating system, in accordance with the present invention, is the provision therein for preventing an excessive voltage across the output terminals 14 and 16 when any of the tubes burn out, or when the electron emission of any of the tubes becomes excessively low. lf, for instance, any one of the heater elements 37 and 39 of the tubes 22 and Z8, respectively, burns out, say, for example, the heater element 37 burns out, then the voltage at the anode of the tube 28 will rise. This condition will cause the tube 44 to conduct more current and, in turn, cause the tube 52 to conduct less current therethrough. A decrease of the current through the tube 52 will result in an increase in the impedance of the control tube 18 by vvirtue of the cathode follower coupling between the tube 52 and the tube 1S and as a consequence, the voltage across the terminals 14 and 16 will be reduced. if the heater element 39 of the tube 28 burns out, a similar set of conditions will result.

if any one of the heater elements 59 and 61 of the tubes 44 and 52 were to burn out, the voltage across the output terminals 14 and 16 would be reduced also. An open in the heater element of either of the tubes 44 and 52 will cause the voltage at the cathode of the tube 52 to drop to ground potential. This ground potential will be applied to the grid of the control tube 1S and the tube 18 will be cut off. Thus, it is seen that if any of the heater elements of the voltage regulating system in accordance with the present invention were to burn out, the output voltage across the terminals 14 and 16 would not increase but rather would decrease, and protect the utilization circuit from an excessive voltage.

Referring now to Fig. 2, there is shown a voltage regulator system substantially similiar to that of Fig. l, except for the circuit between the amplifying regulating system output and the input to the tube 44. In Fig. 2, a sample of the output voltage is obtained from a voltage divider across the output terminals 14 and 16 comprising the resistors 64 and 66 connected in series with the potentiometer 2t). The sample voltage is applied to the grid of an electron tube 68 by means of the variable tap of the potentiometer 20. The anode of the tube 68 is connected to the input terminal 10 through a load resistor 76. The cathode of the tube 68 and the grid of tube 44 are connected to ground through a parallel circuit comprising the capacitor 36 and the voltage regulator tube 34. The anode of the tube 68 is coupled directly to the grid of a tube 72. The anode of the tube 72 is connected to the input terminal 10. The cathode of the tube 72 is connected to ground through a resistor 76 connected in series with a resistor 78. The junction between the resistors 76 and '78 is connected to the cathode of the tube 44. The operation and circuit of the tubes 44 and 52 in Fig. 2 are substantially the same as that described in Fig. 1.

The operation of the voltage regulating system illustrated in Fig. 2 will now be described. Let it be assumed that the output voltage across the terminals 14 and 16 has a tendency to decrease. This decreased, or negativegoing voltage, is applied to the grid of the tube 68. A positive-going voltage from the anode of the tube 68 is then coupled to the grid of the tube 72. This will result in a positive-going voltage being applied to the cathode of the tube 44. In effect, this increases the impedance between the cathode and grid of the tube 44, and the voltage at the anode of the tube 44 will then go more positive. This latter positive-going voltage is applied to the grid of the tube 52, and by cathode follower coupling, this positive voltage is applied to the grids of the series control tube 18. This will cause the impedance of the tube 18 to decrease, whereby a greater voltage will be available across the terminals 14 and 16. Thus, a tendency for the voltage across the output terminals 14 and 16 to fall is offset by a decrease in the impedance of the tube 18, whereby a greater Voltage is made available to the load.

The heater elements 81 and 83 of the tubes 68 and 72, respectively, are connected in series with each other and define a single series circuit with a source of conventional heater voltage (not shown).

The voltage regulating system of Fig. 2 also contains the fail-safe features of the present invention. An open in any of the heater elements S1, 83, 59 and 61 of any of the tubes 68, 72, 44 and 52, respectively, will result in either the reduction of the output voltage or in a removal of the output voltage. For instance, an open in the heater 81 of the tube 68 will cause a zero potential to be applied to the cathode of the tube 44. This is equivalent to raising the voltage on the grid of the tube 44, thereby causing the tube 44 to conduct more current. Consequently, the voltage at the anode of the tube 44 will drop, and this negative-going voltage is applied to the grid of the tube 52. The tube 52 will, in turn, conduct less current, thereby producing a negativegoing voltage at the cathode of the tube 52. This latter negative-going voltage is applied to the grids of the series control tube 18, whereby its impedance is increased and less output voltage is, therefore, available across the terminals 14 and 16.

There has been shown and described herein a voltage regulator system for regulating a unidirectional input voltage wherein the objects of the invention have been achieved. Basically, a sample of the output voltage has been fed back through amplifying means to a third electron tube which had its anode coupled at the grid of a second electron tube which, in turn, had been coupled to the grid of a series control tube by means of a cathode follower circuit. The sample voltage has been applied always to the input circuit of the third tube in such a manner as to vary its plate resistance inversely with the variations in the magnitude of the output voltage.

What is claimed is:

l. In a voltage regulating system of the type having a pair of input terminals for applying a source of unregulated voltage thereacross, a pair of output terminals for applying a substantially regulated output voltage across a load, and a first, variable impedance, grid controlled tube connected between selected ones of said input and output terminals, the combination therewith of a second, variable impedance tube having an anode connected to said one of said input terminals, a grid, a cathode, and a heater element, a cathode resistor connected between said cathode and the other of said input terminals, means connecting said cathode resistor to the grid of said first tube, a third variable impedance electron tube having an anode, a grid, a cathode, and a heater element, an anode load resistor having one end connected to said one of said input terminals, and another end connected to the anode of said third tube and to the grid of said second tube, said heater elements being connected in series, and means to vary the impedance of said third tube inversely with variations in the magnitude of the output voltage across said load.

2. In a voltage regulating system of the type having a pair of input terminals for applying a source of unregulated voltage thereacross, a pair of output terminals for applying a substantially regulated output voltage across a load, and a first, variable impedance, grid controlled tube connected between selected ones of said input and output terminals, the combination therewith of a second, variable impedance tube having an anode connected to said one of said input terminals, a grid, a cathode, and a heater element, a cathode resistor connected between said cathode and the other of said input terminals, means connecting said cathode resistor to the grid of said first tube, a third variable impedance electron tube having an anode, a grid, a cathode, and a heater element, an anode load resistor having one end connected to said one of said input terminals, and another end connected to said anode of said third tube and to the grid of said second tube, said heater elements being connected to each other in series, a voltage divider connected between said output terminals, and means connected between a point on said voltage divider and said third tube to vary the impedance of said third tube inversely with the variations in the magnitude of the voltage at said point.

3. In a voltage regulating system of the type having a pair of input terminals for applying a source of unregulated voltage thereacross, a pair of output terminals for applying a substantially regulated output voltage across a load, and a first, variable impedance, grid controlled tube connected between selected ones of said input and output terminals, the combination therewith of a second, variable impedance tube having an anode connected to said one of said input terminals, a grid, a cathode, and a heater element, a cathode resistor connected between said cathode and the other of said input terminals, means connecting said cathode resistor to the grid of said first tube, a third variable impedance electron tube having an anode, a grid, a cathode, and a heater element, an anode load resistor having one end connected to said one of said input terminals, and another end connected to said anode of said third tube and to the grid 0f said second tube, said heater elements of said second and third tubes being connected in series, means to derive a sample voltage proportional to said output voltage, and means connected between said sample voltage deriving means and said third tube to vary the impedance of said third tube inversely with the variations in the magnitude of said sample voltage, said last-mentioned means comprising fourth and a fifth variable impedance tubes each having an anode, a grid, a cathode, and a heater element, a common cathode resistor connected between the cathodes of said fourth and fifth tubes and said other input terminal, and said heater elements of said fourth and fifth tubes being connected in series.

4. In a voltage regulating system of the type having a pair of input terminals for applying a source of unregulated voltage thereacross, a pair of output terminals for applying a substantially regulated output voltage across a load, and a first, variable impedance, grid controlled tube connected between selected ones of said input and output terminals, the combination therewith of a second, variable impedance tube having an anode connected to said one of said input terminals, a grid, a cathode, and a heater element, a cathode resistor connected between said cathode and the other of said input terminals, means connecting said cathode resistor to the grid of said first tube, a third variable impedance electron tube having an anode, a grid, a cathode, and a heater element, an anode load resistor having one end connected to said one of said input terminals, and another end connected to said anode of said third tube and to the grid of said second tube, said heater elements being connected in series, means to derive a sample voltage proportional to said output voltage, and means connected between said sample voltage deriving means and said third tube to vary the impedance of said third tube inversely with the variations in the magnitude of said sample voltage, said last mentioned means comprising a differential amplifier.

5. In a voltage regulating system of the type having a pair of input terminals for applying a source of unregulated voltage thereacross, a pair of output terminals for applying a substantially regulated output voltage across a load, and a first, variable impedance, grid controlled tube connected between selected ones of said input and output terminals, the combination therewith of a second, variable impedance tube having an anode connected to said one of said input terminals, a grid, a cathode, and a heater element, a cathode resistor connected between said cathode and the other of said input terminals, means connecting said cathode resistor to the grid of said first tube, a third variable impedance electron tube having an anode, a grid, a cathode, and a heater element, an anode load resistor having one end connected to said one of said input terminals, and another end connected to said anode of said third tube and to the grid of said second tube, said heater elements being connected in series, means to derive a sample voltage proportional to said output voltage, and means connected between said sample voltage deriving means and said third tube to vary the impedance of said third tube inversely with the variations in the magnitude of said sample voltage, said last-mentioned means comprising amplifying means having an input circuit and an output circuit, said voltage sample deriving means being connected to said input circuit, said output circuit being connected to said third tube.

6. A regulating system as defined in claim 5 wherein said amplifying means comprises a pair of electron tubes each having a heater element, said heater elements being connected in series and having only one common junction.

No references cited. 

